536 THE LIYEK [CH. XXXV. 



actually produced in the blood. But all recent work shows that the 

 liver is the only place where production of bile occurs, and that in all 

 cases of so-called non-obstructive jaundice, the bile is absorbed from 

 the liver. There may be obstruction present in the smaller ducts, or 

 the functions of the liver may be so upset that the bile passes into 

 the lymph even when there is no obstruction. 



The Glycogenic Function of the Liver. 



The important fact that the liver normally forms sugar, or a 

 substance readily convertible into it, was discovered by Claude 

 Bernard in the following way: He fed a dog for seven days with food 

 containing a large quantity of sugar and starch; and, as might be 

 expected, found sugar in both the portal and hepatic blood. But 

 when this dog was fed with meat only, to his surprise, sugar was still 

 found in the blood of the hepatic veins. Eepeated experiments gave 

 invariably the same result ; no sugar was found, under a meat diet, 

 in the portal vein, if care were taken, by applying a ligature on it at 

 the transverse fissure, to prevent reflux of blood from the hepatic 

 venous system. Bernard found sugar also in the substance of the 

 liver. It thus seemed certain that the liver formed sugar, even when, 

 from the absence of carbohydrates in the food, none could have been 

 brought directly to it from the stomach or intestines. 



Bernard found, subsequently, that a liver, removed from the 

 body, and from which all sugar had been completely washed away by 

 injecting a stream of water through its blood-vessels, contained sugar 

 in abundance after the lapse of a few hours. This post-mortem pro- 

 duction of sugar was a fact which could only be explained on the 

 supposition that the liver contained a substance readily convertible 

 into sugar; and this theory was proved to be correct by the dis- 

 covery of a substance in the liver allied to starch, and now termed 

 glycogen or animal starc'h. We are thus led to the conclusion that 

 glycogen is formed first and stored in the liver cells, and that the 

 sugar, when present, is the result of its transformation. 



Source of G-lycogen. Although the greatest amount of glycogen 

 is produced by the liver upon a diet of starch or sugar, a certain 

 quantity is produced upon a protein diet. It must, then, be produced 

 by protoplasmic activity within the cells. The glycogen when stored 

 in the liver cells may readily be demonstrated in sections of liver 

 containing it by its reaction (red colour) with iodine, and moreover, 

 when the hardened sections are soaked in water to dissolve out 

 the glycogen, the protoplasm of the cell may be so vacuolated as to 

 appear little more than a framework. In the liver of a hibernating 

 frog the amount of glycogen stored up in the liver cells is very 

 considerable. 



